I recently asked a group of about 20 structural engineers in Pittsburgh if they thought that structural engineers have any role in addressing energy code requirements. Less than half of them responded affirmatively – this was apparently the first time that many of them had considered such a notion! So we explored the topic further.
Perhaps the disconnect begins with the way we “frame” our profession (pun intended). If engineers who provide structural services for building design projects identify themselves as the project’s “structural engineer,” it implies their role on the project is limited to ensuring the load-resisting integrity of beams, columns, foundations, the lateral system, and other primary or secondary structural items. The truth is, on most successful building projects with which I have been involved, our role might have been better defined as the project’s consulting structural engineer – implying not just the design of the structural components but a willingness to consult on nonstructural aspects of the project that relate to the building structure. This includes not only deflection and vibration, but acoustics (ever specify an acoustic roof deck?), aesthetics (such as Architecturally Exposed Structural Steel or appearance-grade concrete forms), and yes, the effect of the structure on the thermal performance of the building envelope.
We once worked on a project where our scope carefully limited our role to providing the structural design for wind and gravity load resistance of the building facade elements, specifically excluding any other performance aspects of the exterior envelope. The wall system involved cold-formed steel studs and hat channels, horizontal aluminum channel girts, and thin cementitious rain screen panels. The structural design requirements were met but the energy performance was subpar, primarily due to the thick aluminum girts (aluminum conducts heat about five times better than carbon steel) that thermally bridge across the mineral wool insulation. Because of our carefully worded scope, we were clearly not culpable for the problem. However, we were in as good a position as anyone on the design team to identify this condition as problematic and help develop more appropriate solutions.
Here are a few items to consider:
1. Many structural conditions at a buildings perimeter warrant consideration of thermal transfer effects, including balconies, canopies, lintels, steel-framed roof overhangs, and cold-formed steel framing conditions. These represent opportunities to actively engage with architects, owners, and other members of the design team to address these details, which can lead to very positive results.